1. Field of the Invention
Embodiments of the present invention generally describe achieving fault tolerance in an automated high productivity factory for batch array work-piece handling and processing sized for producing 1,000 or more work-pieces an hour and as high as 40,000 per hour or more. High volume factories require predictable production over some calendar period and require a method of fault tolerance.
2. Description of the Related Art
Solar energy from the sun may be converted to electricity by utilizing a solar power technology called photovoltaics (PV) that uses solar cells tiled into modules. Solar cells produce direct current electricity from the sun's rays, which can be used to power equipment, to recharge batteries, or be converted to AC for on-grid applications.
Increased productivity for manufacturing of PV cells and modules requires batch processing of multiple solar cell work-pieces simultaneously if supply is to meet customer demand. To produce the PV cells and modules, numerous processes may need to be performed upon a work-piece. The work-piece may thus need to be moved from one processing tool to another. A processing tool may comprise one or more chambers coupled together. For example, a processing tool that performs a vacuum based process may comprise one or more processing chambers and one or more load lock chambers coupled together. For a non-vacuum process such as metrology, the processing tool may comprise one or more metrology chambers.
FABs, sometimes referred to as factories, may be set up to arrange all of the necessary processing tools that are needed to process a work-piece into a single processing line. A work-piece exits the processing line after the necessary processes have occurred as a finished product. To increase the output of a FAB, numerous substantially identical processing lines may be present.
At any given point in time, it is not uncommon for a processing tool within a processing line to shut-down for repairs. When any processing tool is shut-down along a processing line, the processing line may shut-down and thus produce no product during the shut-down period. The shut-down thus affects the product output.
For example, suppose a processing tool has a mean time between failures (MTBF) of 320 hours, then a FAB having 50 tools will, on average, have 1 tool shut-down in any 8-hour period. Therefore, when a processing tool is shut-down for an 8-hour period, the processing line containing the shut-down tool is also shut-down for the 8-hour period and thus produces no product. Hence, the processing line has a fault. When a processing line produces no product, the total output of the FAB, as well as the average throughput over a specified period of time, will decrease. Fault tolerance is where a FAB would be able to compensate for a fault while maintaining the desired FAB throughput. It would be beneficial to overcome faults in FABs and still maintain a desired FAB throughput.
Therefore, there is a need in the art for achieving fault tolerance in a photovoltaic FAB.